The present invention relates to an endmill and a cutting method using the endmill and, in particular, a cutting method using a ball endmill and radius endmill.
In general, an endmill is mounted on a main spindle of an NC machining system such as a machining center, and used to create a surface having a three-dimensional complicated shape such as a surface of a metal mold. The endmill is one kind of a milling cutter. Of the endmill, a ball endmill and radius endmill have teeth at a forward tip end in a manner to be continuous from an outer peripheral surface thereof to a tip end and that the tip end also serves a cutting end.
The endmill of such kinds are broadly classified into a solid ball endmill comprised of a single unitary tool of a shank and teeth and a tip-fixed type tool with a teeth-constituting tip brazed or bolted to a tool body.
However, conventional ball endmill or radius endmill has problems as will be set out below.
First, since the cutting speed becomes a substantially zero to a very low speed in the neighborhood of a rotation center of the tip end, there is a risk that no better cutting will be done and a work surface be scraped or peeled.
Further, the pitch of the cutting teeth is narrowed in the neighborhood of the rotation center of the tip end and there is a risk that no better removal of chips will be done and a work surface be damaged.
Further, the solid endmill is expensive because this tool as a whole is made of a rare material. And there is room for improvement in the savings of materials used.
Still further, in a tip-fixed type endmill, for example, plural tips are mounted on the tool body and rotated at high speeds, thus resulting in a variation in the mounting accuracy of the tip end, as well as in the shaping accuracy of the tip itself, exerting a greater adverse effect on the machining accuracy.
The tip-fixed type ball endmill is larger in size and there is a limitation on the rotation speed and hence an inherent limitation on a range in which cutting is made.
The present invention is achieved so as to eliminate drawbacks of a conventional endmill.
The present invention provides an endmill having a shank and a milling head having cutting teeth continuous from a peripheral surface toward a forward tip face, characterized in that the endmill has a through hole extending from the forward tip face of the head to the shank past the head along a rotation axis of the endmill.
A main embodiment of the present invention provides an endmill characterized in that the head and shank comprise separate component parts and the head is mounted on the shank by inserting a screw member from the tip end face into the hole and fixing the screw member to the shank.
In one embodiment, an endmill is provided characterized in that the screw member is completely buried in the head.
In one embodiment, an endmill is provided characterized in that the head has a means for preventing any displacement from the shank.
In one embodiment, an endmill is provided characterized in that the head further has cutting teeth from the outer peripheral surface to a rear end face.
In one embodiment, an endmill is provided characterized in that the head has the forward end face and rear end face formed in a symmetrical way to allow either of cutting teeth on the forward end face side and cutting teeth on the rear end face side to be used.
In one embodiment, an endmill is provided characterized in that the screw member has a discharge hole for discharging a coolant.
In one embodiment, an endmill is provided characterized in that the shank has a diameter smaller than that of the head.
An endmill according to another main embodiment of the present invention, characterized in that the hole extends through the shank. Here, the hole is a coolant passageway for discharging a coolant. In another embodiment, a screw member inserted into the hole to improve rigidity to the ball endmill.
In one embodiment, an endmill is provided characterized in that the cutting teeth is so shaped as to define a curve of a predetermined curvature radius about any given center point in the head.
In one embodiment, an endmill is provided characterized in that the point is located on the rotation axis of the endmill and a sector angle xcex1 connecting an edge of the through hole at the forward end side of the head to the center point of the cutting teeth is 10xc2x0xe2x89xa6xcex1xe2x89xa690xc2x0.
In one embodiment, the cutting tooth has a tip of an ultra-hard sintered body.
In one embodiment, an endmill is provided a coolant discharge passageway provided in the head and shank to allow a coolant to be discharged from between the cutting teeth.
In another aspect of the preset invention, a method is provided for cutting a work with the use of an endmill having a shank and a head having cutting teeth continuous from an outer peripheral surface to a forward end face and a passageway extending from a forward end face of the head past the head to the shank along a center axis of the endmill, characterized by cutting a work surface in a manner to tilt an axis of the endmill at a predetermined angle to the work surface.
The other features and advantages of the present invention will be well understood by referring to those embodiments as will be explained in more detail below.
Further, additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.